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The clinical and histopathological features of herpes zoster (HZ) are usually straightforward. Atypical histological presentations, in the absence of the classical viral cytopathic changes, are well documented and can make the diagnosis of HZ extremely difficult. Herein, we review the existing literature on atypical cutaneous histological manifestations of the disease, with emphasis on the subtle clues, use of immunohistochemistry, and potential pitfalls.

In the UK, sea urchin-related injuries (SUIs) most commonly present in returning travellers. Delayed complications mainly affect the skin but nerves, tendons, joints and bones may also be involved. The management of chronic reactions may be challenging and a variety of approaches have been described. Surgical measures are often undertaken, particularly when retained spines are suspected. We demonstrate, through three cases presenting in the UK with chronic SUIs, that conservative management, surgery and intralesional corticosteroids may all be associated with satisfactory outcomes. Management options should consider the presence of retained spines, injury site, symptoms and importantly, patient preference., (© 2022 British Association of Dermatologists.)

Dermatofibromas are common benign skin lesions, the etiology of which is poorly understood. We identified two unrelated pedigrees in which there was autosomal dominant transmission of multiple dermatofibromas. Whole exome sequencing revealed a rare shared heterozygous missense variant in the F13A1 gene encoding factor XIII subunit A (FXIII-A), a transglutaminase involved in hemostasis, wound healing, tumor growth, and apoptosis. The variant (p.Lys679Met) has an allele frequency of 0.0002 and is predicted to be a damaging mutation. Recombinant human Lys679Met FXIII-A demonstrated reduced fibrin crosslinking activity in vitro. Of note, the treatment of fibroblasts with media containing Lys679Met FXIII-A led to enhanced adhesion, proliferation, and type I collagen synthesis. Immunostaining revealed co-localization between FXIII-A and α4β1 integrins, more prominently for Lys679Met FXIII-A than the wild type. In addition, both the α4β1 inhibitors and the mutation of the FXIII-A Isoleucine-Leucine-Aspartate-Threonine (ILDT) motif prevented Lys679Met FXIII-A-dependent proliferation and collagen synthesis of fibroblasts. Our data suggest that the Lys679Met mutation may lead to a conformational change in the FXIII-A protein that enhances α4-integrin binding and provides insight into an unexpected role for FXIII-A in the pathobiology of familial dermatofibroma., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Mycosis fungoides (MF) is the most common type of cutaneous T-cell lymphoma. Mycosis fungoides classically presents in the skin as patches, plaques, tumors, or erythroderma, progressing to involve the lymph nodes and peripheral blood. The many clinical variants, with different histologic patterns, and the subtle early clinical and histologic changes may delay early diagnosis and present a diagnostic challenge for clinicians. The greatest challenge in diagnosis is the pre-mycotic stage, which may closely resemble eczematous or psoriasiform dermatitis clinically and histologically. The persistence of lesions and inadequate response to treatment are the first warning signs. Later stages of MF have a poor prognosis with poor therapeutic response and fatal outcome. We describe a 72-year-old man, who presented with a two-year history of an unusual eruption, which started on the abdomen, around the waistline, and gradually spread to involve his back, trunk, and buttocks. Clinically, the skin eruption presented as tiger-like stripes. The diagnosis was confirmed after histopathologic examination. The patient was treated with NB-UVB phototherapy with marked improvement.

Background: Few histologic studies describe the histopathologic aspects of scleromyxedema., Objective: We sought to describe the histopathologic and immunohistochemical features of scleromyxedema in a large series of patients., Methods: We studied all the cases with scleromyxedema diagnosed between 2000 and 2014 at participating centers. Sections with hematoxylin-eosin and special stains were examined. Immunohistochemistry for CD3, CD4, CD8, CD20, CD68, and factor XIIIa was performed in 10 cases., Results: A total of 44 skin biopsy specimens from 34 patients were reviewed. Two different histopathologic patterns were observed: the classic microscopic triad (dermal mucin deposition, fibroblast proliferation, fibrosis) was identified in 34 specimens, whereas an interstitial granuloma annulare-like pattern was found in 10 specimens. A superficial perivascular infiltrate with T lymphocytes was found in all specimens whereas an interstitial proliferation of CD68(+) epithelioid cells was identified in the 10 specimens with an interstitial granuloma annulare-like pattern. Elastic fibers were largely lost, explaining the redundant folds of the disease., Limitations: This was a retrospective study., Conclusions: Scleromyxedema shows 2 histopathologic patterns, including the classic type with the microscopic triad of mucin, fibroblast proliferation and fibrosis, and an interstitial granuloma annulare-like pattern. Recognition of these histologic presentations expands the spectrum of scleromyxedema and highlights the difficulty in diagnosing this disabling condition in the absence of a clinicopathological correlation., (Copyright © 2015 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Lymphomatoid papulosis (LyP) is defined as a chronic recurrent skin disease characterized by waxing and waning papules and nodules with histologic features of a CD30-positive T-cell lymphoma. Three histological subtypes (A, B, and C) were already recognized, and only more recently, a further variant simulating histologically an aggressive epidermotropic CD8-positive T-cell lymphoma was described, which was named LyP type D by the authors. We report the case of a 38-year-old woman presenting with a 1-year history of recurrent self-healing papules and nodules, predominantly affecting her upper and lower limbs but also the face, including the lower lip, with no associated systemic symptoms. A biopsy from 1 lesion revealed an infiltrate of atypical lymphoid cells extending throughout the dermis with massive epidermotropism displaying a pagetoid reticulosis-like pattern and a CD8(+)CD30(+) cytotoxic T-cell phenotype. The clinicopathologic features conformed to the newly described type D variant of LyP. Diagnostic studies did not reveal any systemic involvement, and the patient remains otherwise well with no active treatment. In the present report, we discuss the need for clinicopathologic correlation to establish an accurate diagnosis and its importance for an adequate management of these patients.

The clinicopathologic features of 4 AIDS patients with cutaneous colesional Kaposi sarcoma (KS) and cryptococcosis, a rare phenomenon, are described. Biopsies from 3 patients who were highly active antiretroviral therapy (HAART)-naive demonstrated predominant KS with a conspicuous spindle cell component and small aggregates of cryptococcal yeasts in 2 biopsies and predominant gelatinous cryptococcosis with attenuated KS spindle cells in 1 biopsy. One patient was HAART exposed. He had childhood pulmonary tuberculosis, was treated for disseminated cutaneous cryptococcosis 18 months earlier and presented with cutaneous lesions, odynophagia and massive cervical lymphadenopathy in the eighth week of HAART, after achieving viral suppression and a CD4 cell increase from 28 to 184 cells/μL. His skin biopsy demonstrated a dense lymphoplasmacytic infiltrate, neutrophils, and granulomas with admixed aggregates and single Cryptococcus neoformans and focal aggregation of human herpes virus 8-immunopositive spindle cells. Acid fast bacilli were not identified and mycobacterial molecular studies were negative. The features were compatible with cutaneous cryptococcal immune reconstitution inflammatory syndrome. His nodal and oropharyngeal biopsies demonstrated dense mixed, including granulomatous, inflammation with few cryptococcal yeasts and acid fast bacilli, confirmed to be Mycobacterium tuberculosis on polymerase chain reaction testing, without KS. These features were also compatible with immune reconstitution inflammatory syndrome, but the exact role of each infection in the extracutaneous sites was unconfirmed. Colesional KS and cryptococcosis served as the sentinel lesion of AIDS in 3 patients and of immune reconstitution inflammatory syndrome in 1 patient.

Rosai-Dorfman disease (RDD) is a rare but distinctive clinicopathologic entity of unknown etiology affecting lymph nodes as well as extranodal sites. Although cutaneous involvement in RDD is common, purely cutaneous disease is rare and not well documented. We report 22 patients with cutaneous and superficial subcutaneous RDD. The lesions presented as papules and nodules, often with discoloration (9/22) and frequent multifocality (13/22), without predilection for a specific site of the body. Age distribution was wide and ranged from 15 to 68 years, with a median of 43.5 years. Of the 17 patients for whom information on racial background was available, 7 were Asian, 8 were white, and 2 were black, with a marked female predominance (2:1). The lesions resolved in 6 of 13 patients for whom follow-up data were available, regardless of the treatment given. Lesions persisted or recurred in 7 patients. Histologically, the lesions are invariably characterized by a proliferation of polygonal S100-positive histiocytes showing emperipolesis and a mixed inflammatory infiltrate. This study characterizes the histologic spectrum of cutaneous RDD in regard to variation in the numbers of typical S100-positive histiocytes and emperipolesis, variation in the quality and quantity of the inflammatory response, and the degree of stromal fibrosis, which resulted in a strikingly storiform growth pattern in six lesions and a lobulated pattern in two lesions. Whereas the clinical as well as histologic appearance of the cutaneous and subcutaneous lesions in the purely extranodal forms of RDD is indistinguishable from that of systemic RDD, this study emphasizes that purely cutaneous RDD is a distinct clinical entity in regard to its epidemiology and remains localized to the skin even with long-term follow-up. Patients with purely cutaneous RDD are of an older age at onset of disease (median = 43.5 years), with a reversed male/female ratio. There are no significant systemic extracutaneous or serologic manifestations. Whereas systemic RDD is commonly seen in blacks and only rarely reported in Orientals, the majority of the patients in this series with purely cutaneous RDD are Asians and whites.

Aims: Microcystic adnexal carcinoma is a distinctive sweat duct carcinoma of low‐grade malignant potential with a risk for locally destructive growth and local recurrence. Distant metastases and disease‐related mortality are exceptional. The histological hallmarks of these tumours are the diffusely infiltrative growth within the dermis, the frequent invasion of subcutaneous structures, the presence of perineurial invasion, and the bland cytological features. The tumours are organised in cords and strands, and show keratocyst formation and duct differentiation in varying proportions. Marked cytological atypia, nuclear pleomorphism, brisk and atypical mitotic activity and necrosis are not typically seen in these tumours. Methods and results: We report two patients presenting with large, slowly growing tumours on the face showing areas of morphologically high‐grade carcinoma arising on a background of unequivocal microcystic adnexal carcinoma. Both patients are alive with follow‐up of up to 6 years, with no evidence of disease. Conclusions: Morphologically high‐grade transformation in microcytic adnexal carcinoma is a rare phenomenon that does not appear to confer a risk for aggressive behaviour. Recognition depends on sampling of the areas of conventional microcystic adnexal carcinoma. [ABSTRACT FROM AUTHOR]

Amelanotic/hypomelanotic variant of cellular blue naevus (CBN) can present a challenge for the clinician and histopathologist. We report a case of amelanotic/hypomelanotic variant of CBN that presented as a painless scrotal swelling in a child. We review the literature on amelanotic/hypomelanotic CBN, the key histological features and important differential diagnoses. [ABSTRACT FROM AUTHOR]

Cutaneous epitheiloid vascular tumours are heterogeneous groups of vascular proliferations sharing in common the epithelioid morphology of tumour cells. Based on the WHO classification epithelioid vascular tumours are classified on the basis of their biological behavior into benign tumours (epithelioid haemangioma, epithelioid angiomatous nodule) and malignant tumours (epithelioid haemangioendothelioma and epithelioid angiosarcoma). While cutaneous epithelioid haemangioendothelioma affecting only the skin usually but not always follows an indolent clinical course, cutaneous epithelioid angiosarcoma is generally a highly aggressive tumour with dismal prognosis. Also included in this review is pseudomyogenic haemangioendothelioma, a vascular tumour of intermediate (rarely metastasizing) malignancy. It is not traditionally grouped under vascular tumours with epithelioid morphology. Nevertheless, pseudomyogenic haemangioendothelioma is discussed herein because it often contains a proportion of cells with epithelioid morphology, mimicking other epithelioid tumours of different lineage. Correct recognition of cutaneous epithelioid vascular tumours can be difficult due to their overlapping histological features and often absent or limited formation of open vascular spaces, but is crucial for correct management of the patients. In this paper, we review the main clinicopathological and immunohistochemical features of cutaneous epithelioid vascular tumours, including pseudomyogenic haemangioendothelioma, discuss their crucial differential diagnosis, analyze treatment options and prognosis, and give an update on molecular genetic features of this distinctive group of vascular proliferations. [ABSTRACT FROM AUTHOR]

Background Microcystic/ reticular schwannoma is exceptionally rare yet distinctive morphological variant of schwannoma with predilection for visceral sites lacking association with neurofibromatosis. Aims To further delineate clinicopathological features of cutaneous microcystic/reticular schwannoma and to discuss its differential diagnosis. Results We analyzed three cutaneous microcystic/reticular schwannomas, occurring in two males and one female (mean age: 37.6 years). The tumors presented as a non-painful slightly raised papule (mean: 0.7 cm) on upper arm (n = 2) and back (n = 1). No recurrences were observed despite marginal excision (mean follow up: 42 months). Histopathologically, a multilobular proliferation was present in the dermis composed of bland tumor cells forming distinctive microcystic, reticular, lace-like or pseudoglandular structures, containing abundant myxoid/mucinous material. By immunohistochemistry, tumor cells lining microcystic structures corresponded to Schwann cells (diffuse S100 positive, variable GFAP positivity). A discontinuous EMA-positive perineurium was present at the periphery of some of the lobules. Conclusion Cutaneous microcystic/reticular schwannoma expands the spectrum of benign peripheral nerve sheath tumors with reticular morphology encountered in the skin. Other tumors in this group include reticular perineurioma and hybrid tumors with reticular morphology, e.g. reticular perineurioma/schwannoma and reticular perineurioma/neurofibroma. [ABSTRACT FROM AUTHOR]

Aims Unusual cytoplasmic alterations have recently been reported in poorly differentiated cutaneous angiosarcoma, making an accurate diagnosis challenging. As these tumours remain poorly documented, we aimed to study their clinicopathological characteristics more comprehensively. Methods and results Six cutaneous angiosarcomas with unusual cytoplasmic alterations were identified from referral files. All tumours arose as nodules or plaques (range: 05-195 mm) on sun-damaged skin of the head and neck of elderly males (median age: 76.5 years). Histologically, the tumours were composed of enlarged epithelioid cells showing prominent signet ring ( n = 3), foam ( n = 2) or granular cell ( n = 1) change. Vasoformative elements were only focally noted. By immunohistochemistry, all tumours expressed CD31 and avian v-ets erythroblastosis virus E26 oncogene homologue ( ERG). Foam cell change was associated with additional expression of CD68 and CD163. Follow-up (median: 8 months) showed death from disease ( n = 1), death from a gastrointestinal bleed ( n = 1), and a cutaneous metastasis ( n = 1). Only two patients are alive with no evidence of disease. Conclusions Our findings outline the morphological spectrum of cytoplasmic change in cutaneous angiosarcoma. Awareness and a high degree of suspicion in the context of tumours affecting sun-damaged skin of the elderly are necessary to direct appropriate immunohistochemical work-up with inclusion of the endothelial cell markers CD31 and ERG. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented which discusses the case of paranuclear dot-like cytokeratin MBF116 presence in cutaneous myoepithelioma.

The article presents the author's reply to comments made by physician Carlos Diaz-Cascajo on the article on myoid nodules in dermatofibrosarcoma protuberans (DFSP) and its fibrosarcomatous variant. As stated in the paper, authors were at pains to try and exclude that these nodules originated from vessel walls. Aside from simple morphological assessment in this regard, it is notable that such nodules are not desmin positive and that, at least subjectively, these nodules are often greater in number than the usual constituent larger vessels that one would expect in a DFSP.